什么叫共沉淀法?

2025-03-12 01:43:09
推荐回答(2个)
回答1:

共沉淀(coprecipitation),一种沉淀从溶液中析出时,引起某些共存的可溶性物质一起沉淀的现象。共沉淀是重量分析法误差的主要来源之一,主要原因有表面吸附,混晶,包埋等。

吸附共沉淀(adsorption coprecipitation)是由于沉淀表面吸附引起的共沉淀。在沉淀晶格内部,正负离子按照一定的顺序排列,离子都被异电荷离子所饱和,处于静电平衡状态。而处于沉淀表面,棱角的离子电荷未达到平衡,它们的残余电荷吸引了溶液中带相反电荷的离子。沉淀颗粒越小,表面积越大,吸附溶液里异电荷离子的能力就越强。

扩展资料:

减少或消除共沉淀的方法

共沉淀现象是玷污沉淀的主要因素,要通过沉淀反应在溶液中获得绝对纯的沉淀是不可能的。在重量分析中,总是设法减少共沉淀的影响。洗涤是经常采取的措施,它们虽然对减少混晶共沉淀无能为力,却可以有效地减少表面吸附和包藏引入的杂质。较少包埋另一种常用的方法是重结晶。减少或者消除同形混晶最好的办法是实现分离出杂质;对于异形混晶,最好的方法是在沉淀时加入沉淀剂的速度慢,使沉淀进行陈化。

沉淀改变杂质离子存在形式,降低沉淀速度,或采用均相沉淀,都是经常采取的措施,如这些方法不能奏效,还可采取再沉淀的方法。

参考资料来源:百度百科-共沉淀

回答2:

沉淀法通常是在溶液状态下将不同化学成分的
物质混合,在混合液中加人适当的沉淀剂制备前驱
体沉淀物,再将沉淀物进行干燥或锻烧,从而制得相
应的粉体颗粒.根据沉淀方式的不同,其可分为:直
接沉淀法,共沉淀法,均相沉淀法和水解沉淀法等.
直接沉淀法就是使溶液中的某一种金属阳离子
发生化学反应而形成沉淀物,共沉淀法是指在溶液
中含有两种或多种阳离子,它们以均相存在f溶液
中,加人沉淀剂,经沉淀反应后,可得到各种成分的
均一的沉淀,它是制备含有两种或两种以上金属元
素的复合氧化物超细粉体的重要方法

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